A gear motor assembly, such as a window lift drive used in a vehicle to raise or lower a window, typically includes a motor and a gearbox. The gearbox includes a casing and a worm gear disposed in the casing. The motor includes a stator and a rotor. The stator includes a housing with an open end, and an end cap covering the open end of the housing. The rotor is received in the housing and has a shaft with one end extending through the end cap and into the casing. A bearing is mounted on the end cap to rotatably support the shaft. A worm cog, referred to herein after as the worm, in mesh with the worm gear, is mounted on the shaft and rotates with the shaft to drive the worm gear.
As the worm has a diameter larger than a diameter of the inner hole of the end cap, the worm must be mounted to the shaft after the shaft extends through the end cap. However, as the rotor is balanced before being assembled to the end cap, the worm which is assembled latter may adversely affect the balance of the rotor. One option is to eliminate the end cap, but this raises the problem of how to mount the bearing as the bearing is required to support the shaft near the worm to prevent the shaft from bending under the counterforce exerted on the worm by the worm gear during operation.
Therefore, there is a desire for an improved gear motor assembly which can overcome the above described shortcomings.